The present invention relates to a magnetic head for a magnetic disk drive. More particularly, the invention relates to a magnetic recording head structure suitable for a perpendicular magnetic recording type magnetic disk drive in which a magnetic film having an axis of easy magnetization in a perpendicular direction with respect to the surface of a recording medium is to be used therein.
Semiconductor memories and magnetic memories are mainly used in the storage (recording) devices of information apparatus. In terms of access time, semiconductor memories are used as internal storage devices, and in terms of capacity and nonvolatility, magnetic disk drives are used as external storage devices. The recording media of magnetic disk drives use a glass or aluminum substrate, on which magnetic thin films are deposited. A functional section with electromagnetic conversion (i.e., a write functional section) is used to write magnetic information onto such recording media. Also, a functional section (read functional section) that utilizes a magnetoresistive phenomenon or a giant magnetoresistive phenomenon or an electromagnetic induction phenomenon is used to read magnetic information. These functional sections are provided in input/output components called “magnetic heads”.
The storage capacity is an important index expressing the performance of the magnetic disk drive. Along with the development of the information society in recent years, large-capacity and compact magnetic disks are being demanded from markets. Among recording schemes suitable for meeting these demands is a perpendicular recording scheme, which uses the media having an axis of easy magnetization in a perpendicular direction with respect to a recording surface. This scheme allows the enhancement of density, and is therefore considered to prevail in lieu of the conventional longitudinal recording scheme.
Magnetic heads for perpendicular recording are each constructed by forming a read functional section and a write functional section in layered form on a slider. The read functional section has an upper shield and a lower shield, between both of which is sandwiched a reading element having a portion thereof exposed to an air bearing surface. The write functional section has the main magnetic pole piece and subsidiary magnetic pole piece that form a magnetic gap on the air bearing surface side and are magnetically coupled to each other at opposite sides with respect to the air bearing surface. The write functional section also has a coil provided between the main magnetic pole piece and the subsidiary magnetic pole piece.
A recording magnetic field from the main magnetic pole piece acts on a recording medium and reverses the magnetization of a recording layer. For perpendicular magnetic recording, since the magnetic field components in a perpendicular direction need to be used to record, a soft magnetic film, called the soft underlayer (SUL), is provided at a lower portion of the recording layer. The main magnetic pole piece and SUL face each other, and thus a strong magnetic field of the perpendicular field components can be generated. The magnetic fluxes in SUL are returned to the soft magnetic film of the magnetic head that functions as the subsidiary magnetic pole piece, and turn about. Although the soft magnetic film is designed with a great width, the magnetic field is concentrated at the end of the soft magnetic film by a geometrical effect and if its influence is significant, magnetic information may be erased from the recording medium in a wide range.
Patent Document 1 (Japanese Patent Laid-Open No. 2002-100006) discloses a construction where the end of an auxiliary magnetic pole piece (subsidiary magnetic pole piece) on the air bearing surface side is spaced from the air bearing surface. Allowing the auxiliary magnetic pole piece to be spaced apart from the air bearing surface spreads a magnetic gap with respect to SUL present at the bottom of the medium, increases magnetic resistance, and thus allows leakage magnetic fluxes to be reduced.
Stray magnetic fields, however, act not only in a perpendicular direction, but also a horizontal direction to the medium surface. Countermeasures against this problem are disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2002-197619). The technique disclosed therein solves the problem by covering the element that executes reading and writing with a soft magnetic film.
Patent Document 3 (U.S. Patent Application Publication No. 2003/0227714) discloses a structure in which a shield is provided between a coil and an air bearing surface in order to reduce the leakage magnetic field generated from a subsidiary magnetic pole piece during recording.